The present invention relates very generally to an apparatus for cutting foam blocks into predetermined shapes. More particularly, the invention relates to a hot wire apparatus used to accurately cut foam blocks in a pyramidal array; the array being formed for use in conjunction with a microwave system functioning as an electromagnetic wave absorbing material. Although the apparatus of this invention is described primarily in connection with the cutting to form a pyramidal array, it is understood that the principles of the invention may also be applied in the cutting of other predetermined-shaped forms.
The machine described in application Ser. No. 576,484 is used in effectively cutting foam blocks into the desired shape for use as microwave absorbing material. However, now a number of new features have been incorporated and are now described in the new machine the details of which are set forth hereinafter.
In connection with the new features set forth herein, it is an object of the present invention to provide a more universal hot wire machine and one in which more operations can be carried out with substantial simplicity and with minimal operator involvement.
Another object of the present invention is to provide a hot wire cutting apparatus having multiple cutting wires and in which there is preferably independent drive of each of the wires.
A further object of the present invention is to provide a hot wire cutting apparatus in which the foam block support table is movable in a horizontal X axis.
Still another object of the present invention is to provide an improved hot wire cutting apparatus having an improved means for tensioning of the hot wire preferably with the use of a constant torque motor.
Another object of the present invention is to provide a hot wire machine that is operated under software control so as to enable one to use virtually any ratio of vertical-to-horizontal drive. This enables virtually any angle cut when cutting pyramidal-shaped structures.
A further object of the present invention is to provide a hot wire cutting machine having improved wire excitation control. In this regard it is preferred that the control switch associated with each wire now have multiple positions including an automatic position, an on position, and an off position also having associated therewith an indicator light.
Still another object of the present invention is to provide improved control in a hot wire machine including an emergency stop button or switch that enables an operator to stop all action and essentially shut down excitation to the wires under a malfunction condition. In accordance with the invention there is also provided a pyrometer connection which enables the machine to sense an electrical malfunction to stop operation.
Another object of the present invention is to provide a hot wire cutting machine that is operated under software control and operates so that if a wire breaks, the worker can operate the remaining wires manually at each associated switch and thus return to a home position essentially burning the way back through the foam. In this connection, in previous operation when a wire broke, it was necessary to cut through the foam in some manner in order to save the embedded wires.
In accordance with one version of the invention, it is an object hereof to provide the horizontal table with slots for accommodation of the wires, so that wires can burn down past the bottom edge of the material that is being cut. In this connection, there are also provided multiple microswitches on the table to indicate to the computer when wires are over the slots and disallows movement of the X axis of the table while the wires are below the table surface. Other table microswitches are for home (start) position, and at the far right for safety prevention of over travel of the table. Likewise, on the different axes, there are vertical limit switches, one for "home" and one to prevent wires from accidentally reaching the bottom of the slots in the table.
Still another object of the present invention is to provide a hot wire cutting machine in which the table is adapted to progress through one X axis direction with the foam in a first predetermined position and with the table then being rotatable through 90.degree. for transitioning through a second X axis transition to cut the foam in an opposite direction thus forming the pyramidal shapes of the foam block as desired. This multiple cutting operation can be carried out with one single placement of the foam block and with the only operator involvement essentially being at the mid-point of operation and that being of rotation of the table through 90.degree..